An apparatus for movably supporting an article is disclosed, for example, in Japanese Examined Patent Publication (KOKOKU) No. SHO 59-31410 published on Aug. 2, 1984, Japanese Examined Patent Publication (KOKOKU) No. SHO 59-47614 published on Nov. 20, 1984 and Japanese Unexamined UM Publication No. SHO 63-189422 published on Dec. 6, 1988. These publications disclose an article supporting apparatus which includes a bar to be disposed horizontally, and rollers or balls mounted in the bar. The rollers or balls are mounted in such a manner portions thereof protrude above the upper surface of the bar. The bar is raised by a plurality of hydraulic cylinder devices. Another example shown in these publications includes a bar having a plurality of vertical bores arranged in a row. A piston with a ball held on top of the piston is inserted in each of the bores, to provide a cylinder device. The pistons are raised to raise the balls on top of them. Both apparatuses are adapted to support a die on the rollers or balls. A plurality of such bars with the cylinder devices are mounted in a plurality of parallel T-shaped or U-shaped grooves formed in the upper surface of a bolster. By actuating the cylinder devices, the rollers or balls come into contact with the bottom surface of the die disposed on the upper surface of the bolster and raise the die above the upper surface of the bolster. Because rollers or balls support the die, it can be moved with ease.
Prior art apparatuses such as those described in the above-referenced Japanese publications use a bar of which the length corresponds to the depth or width of a bolster and which includes a plurality of rollers or balls or a bar with a plurality of cylinder devices. Therefore, when one or more parts of the apparatus break down, the entire bar including such broken parts must be removed for repair or replacement. Usually, a new bar is replaced in order to reduce the time necessary for repairing the apparatus so that the decrease of the operation efficiency of the press machine may be kept small. However, for ready replacement of a new bar, one or more bars having different lengths have to be stocked, so that the number of bars to be stocked is large. Furthermore, it is usual that the length of bars differs from one press machine to another, and, therefore, it is necessary to manufacture bars for a particular press machine only after a new order is given. Accordingly, it undesirably takes a long time for the ordered apparatus to be shipped.
The described type of article supporting apparatus is used to mount and remove a heavy press die onto and from a bolster, and, therefore, hydraulic cylinder devices are usually used to bear heavy weight. Because of the heavy weight of dies, pneumatic cylinder devices have been hardly used.
Therefore, an object of the present invention is to provide an apparatus for movably supporting an article which can be easily manufactured in a short time, for differing lengths required, and which can be pneumatically operated to support relatively heavy articles.